Chlorination Of Wastewater Research Articles

Removing residual chlorine in water using carbon-based material derived from co-pyrolysis of cotton stalk and desulfurized ash

Herein, an environmentally friendly and low-caste absorbent has been studied to perform with high efficiency and fast removal rate of residual chlorine from wastewater. The chlorine removal absorbent was prepared in situ by co-pyrolysis of desulfurization ash (DA) and cotton stalk (CS) in a tube furnace at 600℃. Compared with CS pyrolysis alone, DA promoted the CS decomposition during co-pyrolysis of DA/CS. The maximum yield of pyrolysis gas was 188 mL/g with 11.33 MJ/Nm3, occurred in the DA/CS blending ratio of 50/100. Moreover, DA also catalyzed the well-developed micropore and mesoporous of cotton-stalk base carbon loaded with DA (CBCDA). The CBCDA with 38.62 wt% DA content had a pore volume of 0.0165 m3/g and a maximum specific surface area of 6.890 m²/g, which 1.96-fold and 1.50-fold higher than that of cotton-stalk base carbon, respectively. The further analysis of adsorption revealed that CaSO3 scattered on the surface of CBCDA fast and efficiently converted hypochlorite ion into chloride ion. The absorbent purified 90.02% residual chlorine from 12 mg/L wastewater within 30 min. Therefore, CBCDA absorbent offers a promising approach for fast and highly efficient purification of residual chlorine in wastewater.

Responses of halophilic microbial communities to changes in salt composition: Comparison between autotrophic nitrification and heterotrophic ammonia assimilation biosystems

The concentration and proportion of chlorine (Cl−) and sulfate ions (SO42−) in actual high salinity wastewater exhibit significant fluctuations due to their diverse sources. This study compared the response of halophilic autotrophic nitrification (AN) and heterotrophic ammonia assimilation (HAA) sludges to changes in salt composition. The results demonstrated that both the AN and HAA systems maintained high ammonia removal efficiency even when exposed to mixed salt ions or pure sulfate conditions. Increasing the concentration of SO42− resulted in an increase in extracellular polymeric substances content, sludge settleability, sludge hydrophobicity, and the relative abundance of Nitrosomonas in the AN system (from 2.3% to 10.4%). The dominant heterotrophic bacteria in the HAA system underwent turnover in response to changes in salt composition conditions. The robustness and the cooperation between microorganisms of the HAA system surpassed those of the AN system. This study provides scientific foundation for treating multi-ion high salinity wastewater.

Application of Nucleotide-Based Kinetic Modeling Approaches to Predict Antibiotic Resistance Gene Degradation during UV- and Chlorine-Based Wastewater Disinfection Processes: From Bench- to Full-Scale.

This study investigated antibiotic resistance gene (ARG) degradation kinetics in wastewaters during bench- and full-scale treatment with UV light and chlorine─with the latter maintained as free available chlorine (FAC) in low-ammonia wastewater and converted into monochloramine (NH2Cl) in high-ammonia wastewater. Twenty-three 142-1509 bp segments (i.e., amplicons) of seven ARGs (blt, mecA, vanA, tet(A), ampC, blaNDM, blaKPC) and the 16S rRNA gene from antibiotic resistant bacteria (ARB) strains Bacillus subtilis, Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae were monitored as disinfection targets by qPCR. Rate constants for ARG and 16S rRNA gene amplicon degradation by UV, FAC, and NH2Cl were measured in phosphate buffer and used to expand and validate several recently developed approaches to predict DNA segment degradation rate constants based solely on their nucleotide contents, which were then applied to model ARG degradation during bench-scale treatment in buffer and wastewater matrixes. Kinetics of extracellular and intracellular ARG degradation by UV and FAC were well predicted up to ∼1-2-log10 elimination, although with decreasing accuracy at higher levels for intracellular genes, while NH2Cl yielded minimal degradation under all conditions (agreeing with predictions). ARB inactivation kinetics varied substantially across strains, with intracellular gene degradation lagging cell inactivation in each case. ARG degradation levels observed during full-scale disinfection at two wastewater treatment facilities were consistent with bench-scale measurements and predictions, where UV provided ∼1-log10 ARG degradation, and chlorination of high-ammonia wastewater (dominated by NH2Cl) yielded minimal ARG degradation.

Ionometric determination of chlorine and fluorine in oil and gas-bearing wastewater

Production and processing of oil and gas are associated with the formation of a huge bulk of wastewater of complex composition disposed in different ways after thorough treatment. Environmental control of the composition and degree of purification of oil and gas-bearing wastewater requires using effective methods for determining various pollutants, including chloride and fluoride. The object of the study was a sample of wastewater from the largest gas field «Mustakillikning 25 yilligi» in the Surkhandarya region of the Republic of Uzbekistan. It is shown that the sample is salty (dry residue is 34.1 – 31.7 g/dm3) and has a neutral reaction. The method of atomic emission analysis of water revealed high concentrations of potassium, sodium and sulfur, a significant amount of calcium and magnesium, and a significantly small number of other elements contained in water. Study of various methods of sample preparation for ionometric measurements of chloride ion showed that a significant proportion of chlorine is bound with organic components of water. It is shown that boiling (~100°C) or fusing at 800 – 850°C with NaOH eliminates the interfering effect of accompanying components (sulfur, iodine and organic matter) on the chloride determination. The results obtained provide quantitative determination of the total content of chlorine in water both in the form of a free chloride ion and in a bound state, probably in the composition of organochlorine compounds. The presence of fluorine in the organic part of the sample has not been revealed. The possibility of using a single sample preparation (boiling or fusing) for the determination of both chloride and fluoride ions has been shown. The interfering effect of the accompanying elements upon fluorine determination was masked by a buffer solution which regulated the total ionic strength. The developed procedures are easy to use, selective, and cost-effective. The correctness and accuracy of the developed techniques were evaluated and proved using a method of varying sample volume.

Influence of the Scheme of Bleaching Hardwood Sulfate Pulp Using Chlorine Dioxide on Chlor-Organic Compounds in Wastewater and Cellulose

Study results of the effect of reducing the steps of the bleaching scheme hardwood sulfate pulp including oxygen-alkaline treatment (OAT) to obtain chlor-organic compounds in filtrates and cellulose. It was determined that a shortened bleaching scheme including oxygen-alkaline treatment would reduce chlorine dioxide consumption by 48 %, to achieve the requirements of best available technologies for the discharge of adsorbed organically bound chlorine in wastewater and the total organic chlorine content in deciduous bleached cellulose.

Environmental impacts of the widespread use of chlorine-based disinfectants during the COVID-19 pandemic.

Chlorinated disinfectants are widely used in hospitals, COVID-19 quarantine facilities, households, institutes, and public areas to combat the spread of the novel coronavirus as they are effective against viruses on various surfaces. Medical facilities have enhanced their routine disinfection of indoors, premises, and in-house sewage. Besides questioning the efficiency of these compounds in combating coronavirus, the impacts of these excessive disinfection efforts have not been discussed anywhere. The impacts of chlorine-based disinfectants on both environment and human health are reviewed in this paper. Chlorine in molecular and in compound forms is known to pose many health hazards. Hypochlorite addition to soil can increase chlorine/chloride concentration, which can be fatal to plant species if exposed. When chlorine compounds reach the sewer/drainage system and are exposed to aqueous media such as wastewater, many disinfection by-products (DBPs) can be formed depending on the concentrations of natural organic matter, inorganics, and anthropogenic pollutants present. Chlorination of hospital wastewater can also produce toxic drug-derived disinfection by-products. Many DBPs are carcinogenic to humans, and some of them are cytotoxic, genotoxic, and mutagenic. DBPs can be harmful to the flora and fauna of the receiving water body and may have adverse effects on microorganisms and plankton present in these ecosystems.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-021-18316-2.

Identification Soybean Processed Waste Environmental Impact and Management Alternatives (Case Study City of Jakarta Selatan)

Processed soybeans such as tempeh and tofu are some of the foods that the people of Indonesia favour. The Tempe and Tofu processing factory produce tofu with the essential soybean ingredients as much as 17 kg every day. The tofu production process starts from soybean immersion, grinding, boiling, filtering, compaction, moulding, cutting, to frying tofu. Production activities from the tofu industry will certainly produce solid and wastewater. These wastes can have a negative impact on the environment. Therefore, the waste must be managed and treated correctly to create an environmentally friendly industry and improve environmental quality. Tofu industry waste management and treatment can be done by identifying the generation of waste that is a priority to be treated and choosing waste treatment technology. There are three alternatives for wastewater treatment from the tofu industry: the chlorine in wastewater, ponds by forming biofilms using biofilter media, and Trickling Filters.

How Surface Water Management Can Benefit Fish Conservation in Urban Streams

Abstract We analyzed 33 y of fish community data collected from a low-order, urban stream in central Illinois, USA, to determine the effects of municipal wastewater management projects and urbanization on fish communities. From 1985 to 2017, species richness, number of pollution-intolerant species, and alternative index of biotic integrity significantly increased at sites across this system. Species diversity likewise increased, but was mostly significant only at sites downstream of the effluent outflow. Ceasing the chlorination of wastewater in 1990 resulted in significant increases in fish community metrics both upstream and downstream of effluent outflow, although effects varied from site to site. Completing a combined sewer overflow abatement project in 2008 resulted in some significant increases in species richness, diversity, and number of pollution-intolerant species at sites downstream of effluent outflow. From 2001 to 2016, the change in the number of pollution-intolerant species correlated inversely with the increased percentage of impervious cover in the study system. There was no significant correlation of other metrics with the change in percent impervious surfaces. These results suggest that urbanization at upstream sites limited to some extent the benefits of water management interventions that improved fish community metrics at downstream sites.

Release and migration characteristics of chlorine during the desulfurization wastewater evaporation process

The spray evaporation technology was a practical approach to realize zero liquid discharge (ZLD). In the evaporation process, the chlorine in desulfurization wastewater would precipitate out and exist in the flue gas, causing a significant impact on the desulfurization system. In this work, the release and migration characteristics of chlorine during the evaporation process were first studied in the lab and pilot-scale platform. The thermal stability of three common chlorine salts was evaluated, and the result indicated that the magnesium salt showed the worst thermal stability, which tended to release chlorine by the effect of hydrolysis. The influences of flue gas temperature, pH value, Cl- concentration of desulfurization wastewater, and gas to liquid ratio were investigated. The results showed that the higher flue gas temperature was conducive to the enrichment of chlorine in the bottom ash; When the pH value of wastewater was adjusted to 9, about 49.8% of gaseous chlorine release could be reduced; Besides, the release of chlorine was also affected by the Cl− concentration of wastewater. In addition, the high gas to liquid ratio led to the higher chlorine release level due to the lift of temperature distribution in the drying tower.

On-site chlorination responsible for effective disinfection of wastewater from hospital.

Both hospital effluent and a model sewage treatment plant (STP) wastewater prepared by mixing STP influent and STP secondary effluent at a volume ratio of 1:9 were directly treated with chlorine for investigation of their effects on disinfection of antimicrobial-resistant bacteria (AMRB) and antimicrobial-susceptible bacteria (AMSB). The overall results indicate that the chlorine disinfection effectively inactivated the majority of AMRB and AMSB, expect for MRSA and Staphylococcus aureus in both wastewaters. No significant differences could further be observed in the taxonomic diversity of micro-organisms after the treatment. The degrees of disinfection given by the direct chlorination were comparable to those attained by combination of conventional activated sludge process and additional chlorine treatment at the STP. The results of this study evoked a recommendation to operate local chlorination treatment directly for the wastewater from medicinal facilities prior to its flow into the STP as sewage. Although additional disinfection treatment at the STP seems necessary to remove the recalcitrant MRSA and Staphylococcus aureus, the present study desirably contributes to a great reduction of the loads of STP and urgent prevention of spreading of infectious diseases in the present state.

In situ electrochemical oxidation in electrodialysis for antibiotics removal during nutrient recovery from pig manure digestate

This study proposed a novel electrodialysis (ED) system, named anode-ED, which can utilise the anode of ED in situ to electrochemically remove the antibiotics during nutrient (N and P) recovery from animal manure digestate. The oxidation of targeted antibiotics (sulfadiazine, SD; and tetracycline, TC) by the anode of ED was first assessed in a single-compartment reactor containing only one pair of ED electrodes. The results showed that Cl2 generated from the anode played the primary role in SD and TC removal. The anode-ED was then established based on a conventional ED process, in which the wastewater successively flowed into the anode compartment and the dilute compartment of the reactor. There was no observable difference in N and P recovery between the anode-ED and conventional ED, while the targeted antibiotics in the anode-ED were removed much more efficiently, with SD and TC removed in the 30 and 60 min, respectively, in comparison with conventional ED. In addition, in the anode-ED, membrane fouling was mitigated due to gas bubbling and the pathogenic microorganism indicators (E. coli and Enterococcus) were inactivated efficiently. Regarding the formation of disinfection by-products, only 134 μg/L of trihalomethanes and 192 μg/L of haloacetic acids were detected in the effluent due to membrane sorption, far less than those generated during conventional electrochemical oxidation and chlorination of wastewater. This study shows that anode-ED is a promising option to remove the antibiotics in an ED system, simultaneously achieving nutrient recovery, antibiotics removal, membrane fouling mitigation and pathogen inactivation.

Novel Disinfection Byproducts Formed from the Pharmaceutical Gemfibrozil Are Bioaccumulative and Elicit Increased Toxicity Relative to the Parent Compound in Marine Polychaetes (Neanthes arenaceodentata)

Formation of halogenated disinfection byproducts (DBPs) from pharmaceutically active compounds has been observed in water supply systems following wastewater chlorination. Although research has been limited thus far, several studies have shown that halogenated DBPs may elicit increased toxicity compared to their parent compounds. For example, the lipid regulator gemfibrozil has been shown to form chlorogemfibrozil (Cl-gemfibrozil) and bromogemfibrozil (Br-gemfibrozil) following chlorination, which are more potent antiandrogens in male Japanese medaka (Oryzias latipes) compared to their parent compounds. In the present study, we aimed to characterize the bioaccumulative ability of halogenated gemfibrozil DBPs in marine polychaetes via chronic sediment exposures and, consequently, to assess the chronic and acute toxicity of halogenated gemfibrozil DBPs through sediment (in vivo) and aqueous (in vivo and in silico) toxicity evaluations. Following 28 day sediment exposures, Cl-gemfibrozil and Br-gemfibrozil bioaccumulated within Neanthes arenaceodentata, with both compounds reducing survival and growth. The biota-sediment accumulation factors determined for Cl-gemfibrozil and Br-gemfibrozil were 2.59 and 6.86, respectively. Furthermore, aqueous 96 h toxicity tests with N. arenaceodentata indicated that gemfibrozil DBPs elicited increased toxicity compared to the parent compound. While gemfibrozil had an acute LC50 value of 469.85 ± 0.096 mg/L, Cl-gemfibrozil and Br-gemfibrozil had LC50 values of 12.34 ± 0.085 and 9.54 ± 0.086 mg/L, respectively. Although acute toxicity is relatively low, our results indicate that halogenated gemfibrozil DBPs are bioaccumulative and may elicit effects in apex food web organisms prone to accumulation following lifelong exposures.

Ready-to-use, functionalized paper test strip used with a smartphone for the simultaneous on-site detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater

The simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater samples was performed. In this report, we designed and fabricated functionalized paper test strips featuring detection zones that use 3-aminopropyltriethoxysilane (APTES) for the immobilization of chromogenic substrates to detect free chlorine, hydrogen sulfide and formaldehyde. After multiple chromogenic reactions, red, blue and purple colors were obtained on the detection zones and analyzed using a smartphone. Under optimum conditions, the paper test strips showed 1.7, 1.8 and 1.7 orders of magnitude for free chlorine, hydrogen sulfide and formaldehyde, respectively. This sensitivity is caused by the formation of homogeneous complexes on detection zones resulting from the chromogenic reagents immobilized on the detection zone via APTES. Through this strategy, free chlorine, hydrogen sulfide and formaldehyde analysis was achieved within 5 min with detection limits of 0.08, 0.14 and 0.13 mg L−1, respectively. The developed paper test strip was able to selective detection of free chlorine, hydrogen sulfide and formaldehyde even in the presence of common interfering agents therefore, the test strip was highly selective. In a further demonstration, the developed functionalized paper test strip was successfully used for simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater in the field and exhibited with high precision and accuracy in detecting free chlorine, hydrogen sulfide and formaldehyde in wastewater samples. Compared to other methods, this assay was advantageous in terms of its low detection limit, time savings, good stability and highly portable format, which facilitates rapid on-site environmental monitoring with a smartphone.

Possible effects of COVID-19 on sustainability of aquatic ecosystems: An overview

Coronavirus is an envelope virus that is persistent in the environment and easily inactivated by the use of chlorine disinfectants. It is a virus novel to human and the first occurrence (SARS-CoV) was detected in Hong Kong in 2003 and a new strain (SARS-CoV-2) in Wuhan, China in 2019. The pandemic had spread throughout the world and is spread through respiratory droplets and fecal-oral routes. The use of chlorine disinfectants has been reported to be the best economic solution to the virus and its use has been on the rise leading to increased wastewater generation. Presently, the existence of coronavirus has been reported in wastewater from indoor and outdoor sources and exposure of the aquatic ecosystem to this elevated concentration of chlorine in wastewater can threaten its sustainability and biodiversity. When aerosols or leakages occur from the sources of wastewater, humans can be infected by the virus by inhaling through the respiratory outlets. This review, therefore, highlights the possible presence and effect of the virus in waste water-based and how the aquatic environment can be sustained.

Experimental study on the evaporation and chlorine migration of desulfurization wastewater in flue gas.

Wastewater from a limestone-gypsum wet desulfurization system cannot be directly reused or discharged due to its high suspended matter content and complex water composition. Desulfurization wastewater evaporation in flue gas is an effective way to dispose wastewater. Multicomponent soluble chlorine salts exist in the desulfurization wastewater. During the evaporation, chlorine enters into the flue gas due to volatilization, which accelerates the enrichment rate of the Cl- concentration in the desulfurization slurry and leads to an increase in wastewater production. This study explored the chlorine migration of various chlorine salt solutions and typical desulfurization wastewater at high temperature during the evaporation process of concentrated wastewater by a laboratory-scale tube furnace and a pilot-scale system. Results showed that when NaCl-evaporated substance was heated, the chlorine ion hardly volatilized. For the evaporated substances of CaCl2 and MgCl2 solutions, some of the crystal water was lost, and hydrolysis occurred to generate gaseous HCl. NH4Cl was easily sublimed, and the decomposition temperature was lowest. A pilot study on spray evaporation of desulfurization wastewater in flue gas showed that the particle size of the evaporated product increased and the main particle size was within 2.5-10μm with increasing flue gas temperature. Increasing the mass ratio of gas to liquid significantly reduced the particle size of the atomized particles, thereby reducing the average particle size of the evaporated particles. The HCl concentration increased with increasing flue gas temperature. When the flue gas temperature was 350°C, the concentration of HCl was 40ppm, and the escape rate of chlorine in the desulfurization wastewater was approximately 30% using typical wastewater from a limestone-gypsum wet desulfurization system.

Wastewater Chlorination for Reuse, an Alternative for Small Communities.

Reuse of wastewater is a practice that has been employed all over the world, mainly in agriculture, where the main aim is to reduce the demand for water and provide nutrients. However, these waters for reuse often have excessive amounts of pathogenic microorganisms, requiring a specific disinfection step even after being subjected to a purification process. Thus, this research aimed to evaluate the potential use of calcium hypochlorite and sodium hypochlorite as disinfectant agents for the sanitary effluent of the treatment system based on constructed wetlands for later reuse. Disinfection tests were carried out in batch, using three dosages of hypochlorite (5, 10 and 15 mg.L-1) and different contact. In all disinfection tests, inactivation of indicator microorganisms (total coliforms and E. coli) was considered effective for the two disinfectant agents adopted, satisfying the criteria for reuse according to the World Health Organization (WHO). There was no formation of trihalomethanes after disinfection tests.

Electron donating capacity reduction of dissolved organic matter by solar irradiation reduces the cytotoxicity formation potential during wastewater chlorination

After treated wastewater is discharged into surface water for unplanned indirect potable reuse, solar irradiation transforms the dissolved organic matter (DOM), which would alter the formation of disinfection byproducts (DBPs) and change the cytotoxicity formation potential (CtFP) during post–chlorination in drinking water treatment plants. This study investigated the effects of solar irradiation on the CtFP and total organic halogen formation potential (TOXFP) of wastewater during post–chlorination. Exposure to natural sunlight decreased the formation potential of cytotoxicity to Chinese Hamster Ovary cells. Under 24 h simulated solar irradiation, CtFP and TOXFP decreased by more than 40%. X–ray photoelectron spectra and Fourier transformation infrared spectra suggested solar irradiation destroyed the key DBP precursors containing phenolic hydroxyl moieties (Ph–OH). The destruction of Ph–OH under solar irradiation was reflected by a decrease in the electron donating capacity (EDC) of DOM and the post–chlorination decreased the EDC further. Increasing the irradiation–consumed EDC abated the chlorine–consumed EDC, while the chlorine–consumed EDC was positively correlated to the CtFP and TOXFP by means of the electrophilic substitution–aromatic ring cleavage. Solar irradiation thus reduced the CtFP and TOXFP in wastewater during post–chlorination. This study revealed that solar irradiation decreased the risks of treated wastewater for unplanned indirect potable reuse and provided a strategy of controlling CtFP and TOXFP via reducing EDC of DOM in pretreatments.

Mystery of the high chlorine consumption in disinfecting a chemically enhanced primary saline sewage

Stonecutters Island Sewage Treatment Works is one of the largest sewage treatment plants in the world and consists mainly of a chemically enhanced primary treatment (CEPT) unit and a disinfection unit. It has long been realized that most of the dosed chlorine (15 mg/L) is lost at the beginning part of the disinfection unit during disinfection of the CEPT effluent. Lab-scale tests were therefore conducted in this study to determine the causes. Because ferric chloride is used in CEPT, ferrous iron in the CEPT effluent (from the reduction of ferric iron) was initially thought to be the main chlorine consumer. However, the chlorine consumption by ferrous iron was found to be 1.2 mg/L at most. Suspended solids and sulfide also did not contribute significantly to the chlorine consumption. Batch tests were therefore conducted to evaluate the effects of mixing condition and chlorine stock solution concentration on the chlorine consumption. Less chlorine was consumed upon increased mixing. Using a high-concentration chlorine stock solution (25000 mg/L) resulted in a 3-times-higher chlorine consumption in the absence of mixing than using a low-concentration chlorine stock solution (2500 mg/L). By correlating the losses of ammonia and total nitrogen with the chlorine consumption, we hypothesized that the use of a high-concentration chlorine stock solution under poor mixing leads to a localized high ratio of chlorine to ammonia, resulting in breakpoint chlorination and an unusually excessive chlorine consumption. A novel apparatus was developed to quantify the nitrogen gas generated during chlorination of a simulated wastewater, and the mass balance of nitrogen-containing species (i.e., ammonia, nitrogen gas, nitrite and nitrate) during the chlorination was inspected. The good fit between the measured chlorine consumption and that back-calculated from nitrogen-containing species verified our hypothesis. Finally, it needs mentioning that the high chlorine consumption and the breakpoint chlorination may occur during chlorine disinfection of any sewage effluents with relatively high ammonia levels; thus it is suggested that either not-too-high concentrations of chlorine stock solutions or sufficient mixing should be applied during disinfection of the sewage effluents.

The impact of disinfection Ct values on cytotoxicity of agricultural wastewaters: Ozonation vs. chlorination

Toxicity arising from toxic disinfection byproducts is an unintended result of disinfection during water reclamation. To ensure safe water reclamation treatment, it is important to develop a disinfection strategy with minimal formation of overall toxicity in the reclaimed water. The cumulative disinfectant concentration over time (Ct) is a useful concept for pathogen control during reuse water disinfection. We evaluated the toxicity impact of Ct values and different methods to achieve identical Ct values by ozonation or chlorination of wastewaters from four agricultural sources on mammalian cells. N-acetylcysteine (NAC) reactivity of the wastewater organic extracts was determined to reveal their impact on the thiol-specific biological detoxification mechanism. The results demonstrated that for two sources and for both ozonation and chlorination, higher Ct values enhanced cytotoxicity. The ozonated waters were at least 10% less toxic and as much as 22.4 times less toxic than either the non-disinfected controls or the chlorinated waters. Chlorination consistently induced higher cytotoxicity than ozonation by between 2.2 and 22.4 fold, respectively, and induced similar or higher cytotoxicity than the non-disinfected controls, by at most 4.4 fold. Given the same Ct values, the combination of high disinfectant concentration and short contact time produced finished wastewaters with higher toxicity, than the combination of low disinfectant concentration and long contact time. NAC thiol reactivity was positively and significantly correlated with mammalian cell cytotoxicity, and agreed with 80% of the cytotoxicity rank order. This suggests that the induction of cytotoxicity involved reactions with agents that acted as thiol pool quenchers. The overall results indicate that the cytotoxicity of wastewaters may increase when higher Ct values are applied to inactivate recalcitrant pathogens. To counteract the potential increase in cytotoxicity at high Ct values, for both ozonation and chlorination, lower disinfectant dose and longer contact time may be adopted.

Chlorine Demand and Trihalomethane Formation during Chlorination of Wastewater in Hillsborough County, Florida: Effects of Temperature and Chlorine Dose

AbstractThe Northwest Regional Water Reclamation Facility (NWRWRF) in Hillsborough County, Florida, is considering whether to switch from disinfection via ultraviolet (UV) radiation to disinfection...